A gel base prepared by increasing the viscosity of an aqueous carboxyvinyl polymer solution with a basic viscosity-increasing agent such as sodium hydroxide, triethanolamine, diisopropanolamine, etc. has such excellent characteristics that (i) since the stock polymer has a high purity and uniform quality, it can give a topical preparation with a high reproducibility, (ii) it shows almost a constant viscosity in the range of a temperature of from 10.degree. to 70.degree. C., (iii) it is hardly decomposed with microorganisms such as bacteria, (iv) the gel is stable in a wide range of pH, and the like, and hence, it has been used for preparing various topical preparations such as medicines, cosmetics, etc. However, the gel base has such defects that the viscosity thereof is decreased by irradiation with a light (ultraviolet light), and it shows low storage stability, and further that it is restricted in the utility. When the above-mentioned conventional basic viscosity-increasing agents are used, it must be adjusted to pH 10 or higher in order to eliminate the above defects. An ointment having pH 10 or higher shows high irritation to mucous membranes and skin which is not tolerable.